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Serving Content Using a Fully Managed Reverse Proxy Architecture in AWS
With the trends to autonomous teams and microservice style architectures, web frontend tiers are challenged to become more flexible and integrate different components with independent architectures and technology stacks. Two scenarios are prominent:
- Micro-Frontends, where there is a single page application and components within this page are owned by different teams
- Web portals, where there is a landing page and subsections of the presence are owned by different teams. In the following we will refer to these as components as well.
What these scenarios have in common is that they consist of loosely coupled components that are seamlessly hidden to the end user behind a common interface. Often, a reverse proxy serves content from one single entry domain but retrieves the content from different origins. In the example in Figure 1 (below) we want to address one specific domain name, and depending on the path prefix, we retrieve the content from an on-premises webserver, from a webserver running on Amazon Elastic Cloud Compute (EC2), or from Amazon S3 Static Hosting, in the figure represented by the prefixes /hotels, /pets, and /cars, respectively. If we forward the path to the webserver without the path prefix, the component would not know what prefix it is run under and the prefix could be changed any time without impacting the component, thus making the component context-unaware.
Figure 1: Architecture, AWS Amplify Console
Some common requirements to these approaches are:
- Components should be technology-agnostic, each component should be able to choose the technology stack independently.
- Each component can be maintained by a dedicated autonomous team without depending on other teams.
- All components are served from the same domain name. For example, this could have implications on search engine optimization.
- Components should be unaware of the context where it is used.
The traditional approach would be to run a reverse proxy tier with rewrite rules to different origins. In this post we look into managed alternatives in AWS that take away the heavy lifting of running and scaling the proxy infrastructure.
Note: AWS Application Load Balancer can be used as a reverse proxy, but it only supports static targets (fixed IP address), no dynamic targets (domain name). Thus, we do not consider it here.
AWS Amplify Console
The AWS Amplify Console provides a Git-based workflow for hosting fullstack serverless web apps with continuous deployment. Amplify Console also offers a rewrites and redirects feature, which can be used for forwarding incoming requests with different path patterns to different origins (see Figure 2).
Figure 2: Dashboard, AWS Amplify Console (rewrites and redirects feature)
Note: In Figure 2, <*> stands for a wildcard that matches any pattern. Target addresses must be HTTPS (no HTTP allowed).
This architectural option is the simplest to setup and manage and is the best approach for teams looking for the least management effort. AWS Amplify Console offers a simple interface for easily mapping incoming patterns to target addresses. It also makes it easy to serve additional static content if needed. Configuration options are limited and more complex scenarios cannot be implemented.
If you want to rewrite paths to remove the path prefix, you can accomplish this by using the wildcard pattern. The source address would contain the path prefix, but the target address would omit the prefix as seen in Figure 2.
When looking at pricing compared to the other approaches it is important to look at the outgoing traffic. With higher volumes, this can get expensive.
Amazon API Gateway
Amazon API Gateway is a fully managed service that makes it easy for developers to create, publish, maintain, monitor, and secure APIs at any scale. API Gateway’s REST API type allows users to setup HTTP proxy integrations, which can be used for forwarding incoming requests with different path patterns to different origin servers according to the API specifications (Figure 3).
Figure 3: Dashboard, Amazon API Gateway (HTTP proxy integration)
Note: In Figure 3, {proxy+} and {proxy} stand for the same wildcard pattern.
API Gateway, in comparison to Amplify Console, is better suited when looking for a higher customization degree. API Gateway offers multiple customization and monitoring features, such as custom gateway responses and dashboard monitoring.
Similar to Amplify Console, API Gateway provides a feature to rewrite paths and thus remove context from the path using the {proxy} wildcard.
API Gateway REST API pricing is based on the number of API calls as well as any external data transfers. External data transfers are charged at the EC2 data transfer rate.
Note: The HTTP integration type in API Gateway REST APIs does not support forwarding trailing slashes. If this is needed for your application, consider other integration types such as AWS Lambda integration or AWS service integration.
Amazon CloudFront and AWS Lambda@Edge
Amazon CloudFront is a fast content delivery network (CDN) service that securely delivers data, videos, applications, and APIs to customers globally with low latency and high transfer speeds. CloudFront is able to route incoming requests with different path patterns to different origins or origin groups by configuring its cache behavior rules (Figure 4).
Figure 4: Dashboard, CloudFront (Cache Behavior)
Additionally, Amazon CloudFront allows for integration with AWS Lambda@Edge functions. Lambda@Edge runs your code in response to events generated by CloudFront. In this scenario we can use Lambda@Edge to change the path pattern before forwarding a request to the origin and thus removing the context. For details on see this detailed re:Invent session.
This approach offers most control over caching behavior and customization. Being able to add your own custom code through a custom Lambda function adds an entire new range of possibilities when processing your request. This enables you to do everything from simple HTTP request and response processing at the edge to more advanced functionality, such as website security, real-time image transformation, intelligent bot mitigation, and search engine optimization.
Amazon CloudFront is charged by request and by Lambda@Edge invocation. The data traffic out is charged with the CloudFront regional data transfer out pricing.
Conclusion
With AWS Amplify Console, Amazon API Gateway, and Amazon CloudFront, we have seen three approaches to implement a reverse proxy pattern using managed services from AWS. The easiest approach to start with is AWS Amplify Console. If you run into more complex scenarios consider API Gateway. For most flexibility and when data traffic cost becomes a factor look into Amazon CloudFront with Lambda@Edge.